I'm probably going to get chewed out for this, but here goes. Density x mass = weight. In the Diamond tables, the cue balls are separated by density. The red or blue circle cue balls separate the best, because they have the highest density readings, meaning the hardest cue balls. The measle cue ball won't separate very well because it's not as hard as the red/blue circle cue balls. Now, what does that mean? Well, it means that the red/blue circle cue balls have a harder mass than the measle cue ball, and therefor have a slightly higher weight for the same mass, but not really noticeable, but, the higher density cue balls because of their density require a little more force to draw back that same mass, while follow english is more effected. Density is why the Diamond tables can not separate the Arimuth Premier or Premium object balls, because they have almost the same density as the red/blue circle cue balls, while the Super Arimuth Pro sets of balls, as well as the Arimuth standard balls will work just fine.
So, to sum this all up, the measle cue balls, which was designed to show the viewing audience the spin of the cue ball, has a softer/less dense substance than the red/blue circle cue balls, therefor easier to draw, harder to follow, break out racks. While the red/blue circle cue balls, with a higher density, draw a little harder, yet follow easier with less effort, break racks and clusters easier.
Just my understanding of the density of object balls. One other thing, the one balls in most all sets of balls, have a higher density reading than the rest of the object balls in the set, as the one ball is more designed to take the impact of the break more than any other ball.
Try this for a test. Rack the balls with the one ball up front, break the balls as you normally would. Notice how they break apart/8 ball. Then re-rack the balls using any other ball for the point ball, break them again, do this several times, and you'll see that the balls break better using the one ball up front as opposed to any other balls. It's because the one balls density that it don't absorb the hit of the cue ball, therefor transferring more of the energy of the break to the rest of the object balls, giving you a better spread of the break.
Glen